This invention pertains to novel fluoride ion-releasing polymerizable acrylic and methacrylic acid derivatives, and to their preparation and use in fluoride-ion releasing resins which have use in dental applications.
The fluoride ion has long been recognized as an effective agent for reducing carious attack and demineralization of tooth structure. For this reason, there has been interest in incorporating fluoride ion in dental materials.
The most widely used fluoride-containing substances added to dental resin materials are sodium fluoride, stannous fluoride, and certain ammonia fluorides. Attempts have been made to incorporate such inorganic fluoride salts into cavity liners, sealants, coatings, orthodontic bracket adhesives and amalgams. However, a primary problem with incorporation of inorganic fluoride-containing salts into dental resins is an inherent incompatibility caused by a large difference in polarity between the ionic fluoride salt and the low-polarity dental resin, the latter being an organic material. Incompatibility usually causes phase separation with the resin, loss of mechanical integrity of the resin and rapid fluoride ion release within the first few hours of use. Incorporation of low molecular weight organic fluoride species has a plasticizing effect which leads to similar undesirable results.
Kadoma et al., Macromol. Chem. 1981, 182, 273 and Macromolecules 1982, 15, 1119, synthesized a fluoride ion releasing methacryloyl fluoride-methylmethacrylate copolymer, in which the fluorine is covalently bonded to a carbonyl group. This resulted in the slow release of the fluorine as fluoride ion by hydrolysis of the acid fluoride in aqueous solution. It has been shown that this copolymer can be incorporated into experimental sealants and will release fluoride slowly. Tanaka et al., J. Dent. Res. 1987, 66, 1591; and Nishida et al., JP 62-012,706 (1987).
Rawls et al., U.S. Pat. No. 4,515,910 (1985) and U.S. Pat. No. 4,572,920 (1986), incorporated fluoride ion as a mobile charge into an acrylic anion exchange resin. These studies demonstrated that t-butylaminoethyl methacrylate hydrogen fluoride can be copolymerized readily with other acrylic monomers and can serve as a source of fluoride ion in the final resin. These resins were tested as fissure sealants, orthodontic cements and resin materials.
In light of this background there remains a need for further compounds which can be used in the preparation of fluoride ion-releasing dental materials. Desirably, the compounds would be prepared from readily available starting materials, and provide dental materials with acceptable levels of sustained fluoride ion release while exhibiting acceptable hardness and resistance to deterioration. The present invention addresses these needs.